Industrial waste compactors normally utilize an hydraulically operated ram assembly in combination with a container. The ram is reciprocal for transferring waste from a charge box into the container in which the waste is compressed. The container may be removable from the ram assembly.
The compactor is typically located at a facility remote from the place at which it is to be emptied. There is usually a fee imposed for emptying the container, regardless of the degree to which the container is filled. Economics suggest that the container not be emptied until it has been filled, because to empty a partially filled container will unnecessarily increase costs for the user. These costs include not only the "tipping" fee for emptying the container, but also the cost for transporting the container to the place at which it is to be tipped. Most users of compactors are therefore interested in seeing to it that the container is not emptied until it has achieved a sufficient level of fullness, and so various fullness monitors have been proposed for that purpose.
The compaction of waste by a reciprocating hydraulic ram is a relatively uncontrollable activity on account of numerous factors. When a variable pressure pump is utilized, as in most large compactors, the output pressure is a function of the resistance exerted against the ram as it transfers the waste into the compactor in order to cause compaction. This resistance is not however uniform, and the ram pressure will typically experience a number of pressure excursions throughout the filling sequence. For example, the pressure output is relatively constant when the container is empty, because then the ram is merely pushing the waste into an empty container so that there is essentially no resistance applied. The transferred waste also initially tends to lie upon the floor of the container until the length of the container is filled. Once the floor has been filled, then at some point the column of waste breaks and some is then forced above that which preceded it. This filling and breaking cycle continues to occur as the container becomes filled, with the result that the pressure is elevated before the column breaks and then is reduced as the next column builds. Yet a further factor has to do with the compressibility of the waste, because it is not unusual for drums, pallets, boards, and like material to be deposited in the charging box. These materials will typically resist being compressed or broken until some limit is exceeded, with the result that the pressure before compression or breakage exceeds that after the event. Various other factors have an impact on the pressure which must be applied to the ram, such as the temperature of the hydraulic fluid, the type of material being compacted, and the like. Each of these factors has a somewhat unpredictable impact on the output hydraulic pressure, thereby complicating the task of trying to monitor the fullness of the container.
Various means have been proposed for monitoring the fullness of the container throughout the filling sequence. It has been proposed, for example, to utilize a pressure switch in the hydraulic line to measure the pressure exerted by the waste when the ram is in the extended or waste compacting position. Various devices have also been proposed for use within the container for monitoring fullness, but anything positioned within the container is subject to being damaged or interfered with as the container fills. It has also been proposed to monitor the hydraulic pressure or the motor current of the hydraulic pump during each reciprocation of the ram. Monitoring motor current or hydraulic pressure is not, however, an accurate means of determining fullness when the container is relatively empty, so that the fullness information may be quite inaccurate during the beginning of the filling cycle.
Those skilled in the art will appreciate that there is a need for a compactor fullness determining system which is able to accurately determine container fullness during all phases of the filling process. The system should be able to know when the container has been emptied in order to differentiate between a container which is empty and one which has recently experienced a downward pressure excursion. The disclosed invention meets these criteria, and also provides a local indication of the container fullness so that the operator may monitor the filling process.